1991 240 Fuel Pump Mystery

Hiya guys

Okay so, I have this 1991 245 that has developed an intermittent stalling/no start issue. I have so far figured out that it is the fuel pump...when I put in the key and don't hear it hum, the car won't start. Sometimes it hums, sometimes it doesn't. Sometimes it hums and then it starts and runs for a couple of seconds and then it stalls out and I'm not hearing the hum anymore.

"Jumper the #4 and #6 fuses!" the internet helpfully offers. "If the fuel pump kicks in, your fuel pump relay is bad!" Well sure enough, when I attach alligator clips to those two the fuel pump kicks on and I can drive it just fine with no stalling. So I bought a brand-new relay from DaveBarton.com and...the problem persists.

At this point I am suspecting the ECU, but that is a new level of expense with the whole "replace the part and see what happens" technique, so I thought I'd ask y'all if that's very likely to be it, or if there are other elements in the chain between those two fuses that could be causing it. This is the first car I've ever worked on and my troubleshooting ability is limited so I am wondering if this is the right point to let a mechanic have at it...or if it really will be simply plug-n-play ECU replacement.

Thoughts? Thanks.

where are you located? Someone could have an ECU you could simply test for free.99

Welcome to the forum

I am in southern New Hampshire.

Thank you for the welcome!

When my daughter's car was acting very flaky, occasional stalss and no-starts, and the fuel pump itself was buzzing and acting funny, it ended up being a loose wire under the hood. There was a single separate wire that attached to the positive battery terminal that powered the whole fuel injection system. It was loose, and the resulting low and erratic voltage/amperage that made it through to the Bosch parts collection created all sorts of odd issues.

So you might check that wiring, and the single corrosion prone fuse in it, first? And use a multimeter to make sure you have a good 12V+ where it's supposed to be on the relay.

PS: I once spent an embarrassing amount of time trying to troubleshoot my old 1800E for the same issue. I messed around with the pump relay. I messed around with the pump wiring. I messed around with the pump. Ended up being that single wire leading to the positive battery terminal had just broken off.

Maybe someone will chime in.

There should be an LH 2.4 diagram on kjet.org in the greenbooks section. One thing you could do is get a multimeter or test light and hook it up in parallel with the wire that LH grounds to trigger the relay. If it stays grounded the whole time, while the car stalls, you may need to look elsewhere.

Is your car a 5speed or auto? It could be LH 2.4 or 3.1 if manual - definitely 2.4 if automatic. I'm pretty sure the pinouts are the same enough for this test.

Also, you could hook a switch to the dash to ground the relay in the interim - then you'll have to trigger the fuel pumps yourself, but you'll get where you need to go.

Edit: good point from johnMc - that fuse up there corrodes and sucks bigtime

Thanks guys I appreciate the advice. I know nothing about multimeters and voltage testing but a friend of mine knows a fair deal about electronics so I will enlist his help. Oh and mine is an automatic transmission.

Could be a bad ground. The fuel pump runs if the fuses are jumped? Or are we talking about the fuel relay? Is the power at the fuses good? I would say track it backward. There is either a wire fault or abad fuseblockor relay. It is not the ecu if everything runs when you jump the fuse/relay.

Yeah I am attaching an alligator-clip wire to the left side tab of fuses #4 and #6 and start right up and drive around without stalling.

ECU is behind the kick panel, passengers side, just to the right of your feet if you're sitting in the seat. Pink-label -561 ECU is failure prone, white label 561 is better, white label 951 is best. If none of those, could be an EGR car, or even LH3.1 (-572 ECU, brown or white label, also somewhat failure prone in my experience).

Check which ECU your car has and report back. It could be the issue, but I don't know exactly how to rule it out, so I'd be parts swapping to diagnose. 951 ECUs can be bought for ~$50-100 and rarely seem to fail.

luchy72v said:

Yeah I am attaching an alligator-clip wire to the left side tab of fuses #4 and #6 and start right up and drive around without stalling.

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Try this: attach your alligator clip from fuse 6 to fuse 6. Yes, I mean from one side of the fuse to the other - clipped to the fuse holder of course.

Or when it stalls, check for fuse 6 being hot due to poor contact.

The "unreliable" fuse under the hood was moved to the #6 position inside the car for MY 1991, and my opinion is that introduced a new mode of unreliability that remained until mid-production 1993.

Doing the above test is easy, cheap, and conclusive. If the symptom remains, there's another spot above the passenger's left knee in the 12-pin cabin harness plug, but that's step 2 and maybe the ECU is step 3 - verified by supplying ground to the blue/green wire at the relay.

Yes, it could be the ECU, but in my experience, when the pink label syndrome rears its head it does so permanently. What I refer to here is the lack of fuel pump relay ground supplied at ECU pin 20, not any of the other foibles folks ascribe to the 561.

UPDATES:

1. Checked out the ECU and.....the notorious pink-label 561.

2. I jumpered from #6 to #6 and the car started right up. I did a bunch of laps around my cold, dark neighborhood, didn't want to wander far in case I got stranded...maybe a total of 5 miles in 20 minutes, with lots of bumps and stop signs and at one point pulled over and turned the car off and it restarted right back up. However for the last half-mile or so I yanked the clips back off and it continued to run fine...such is the nature of an intermittent problem. On wednesday I might attempt to drive all the way to work (35 highway miles) and see how it goes.

JohnMc said:

When my daughter's car was acting very flaky, occasional stalss and no-starts, and the fuel pump itself was buzzing and acting funny, it ended up being a loose wire under the hood. There was a single separate wire that attached to the positive battery terminal that powered the whole fuel injection system. It was loose, and the resulting low and erratic voltage/amperage that made it through to the Bosch parts collection created all sorts of odd issues.

So you might check that wiring, and the single corrosion prone fuse in it, first?

Click to expand...

From what I understand, that fuse had been moved to the interior fusebox by the time my '91 was built. I looked around and did not see anything that looked like the wire you describe or a fuse holder.

A scanned 2.4 greenbook is at http://www.volvowiringdiagrams.com/volvo/LH 2.4/LH2.4 Manual Complete.pdf, it sounds as though you may have found the problem, aside from that pink-labeled 561 ECU.

cleanflametrap said:

Try this: attach your alligator clip from fuse 6 to fuse 6. Yes, I mean from one side of the fuse to the other - clipped to the fuse holder of course.

Or when it stalls, check for fuse 6 being hot due to poor contact.

The "unreliable" fuse under the hood was moved to the #6 position inside the car for MY 1991, and my opinion is that introduced a new mode of unreliability that remained until mid-production 1993.

Doing the above test is easy, cheap, and conclusive. If the symptom remains, there's another spot above the passenger's left knee in the 12-pin cabin harness plug, but that's step 2 and maybe the ECU is step 3 - verified by supplying ground to the blue/green wire at the relay.

Yes, it could be the ECU, but in my experience, when the pink label syndrome rears its head it does so permanently. What I refer to here is the lack of fuel pump relay ground supplied at ECU pin 20, not any of the other foibles folks ascribe to the 561.

Click to expand...

Can you elaborate on the alligator clip method? Are you simple making a jumper to connect both sides of the number 6 fuse holder...if so are you saying to leave the fuse in place, or remove it and jumper the connection? Would you recommend putting an inline fuse into the fab'd jumper wire?

I am having a similar problem with my son's 93 240...warm, low speed stalls and trouble with warm engine restarts (stalls when reversing). The fuse holder for #6 is a bit scorched and feels a little warm. The fuel pump relay is a little warm, too. I am thinking resistance in wiring somewhere or a fuel pump going down.

I'll see what ECU he has. Not sure what month the car was built, but I can check that, too.

luchy72v said:

From what I understand, that fuse had been moved to the interior fusebox by the time my '91 was built. I looked around and did not see anything that looked like the wire you describe or a fuse holder.

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I'm sure CFT has a much better handle on the year to year changes. My 240 sample pool is very small.

JohnMc said:

I'm sure CFT has a much better handle on the year to year changes. My 240 sample pool is very small.

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John, I still have 8 of them between our 4 and 4 belonging to kids and grandkids. So far though, I'm the only one for whom the "maintenance & nonperformance" aspect of Volvo ownership sparks any real interest. Time for me to consider a smaller pool, maybe.

Your Classic, though highly modded... did that originally fall under the PAL fuse change mid-year in '93? I've only seen 92's and 93's in the yards -- never owned one. Either way, IMO they never got that circuit right.

Yes, it has a separate fuse box with the large PAL fuses on the positive battery terminal. This splits off most of the heavy loads from the rest of the car electrical ssytem right at the source.

I removed it for a little bit when I put the battery in the trunk, then I moved it back up front (using a cute little Braille battery), although now I've re-purposed them to run other things (the e-fan, a clean power source for the engine electronics, etc).

I'd guess the PAL fuses were probably an improvement. They're more suited to handling the amperage the fuel pumps used. But they're not really weather proofed very well, and they were still out under the hood in the elements, not inside and dry.

My daughter's car was a 1990, and it had the fuse up near the battery. And the wire from the fuse lead straight to the positive battery terminal, where it was loose. The resulting varying amount of current that made it through to power the injectors/fuel pump/two ecus lead to some rather random symptoms. I bought a new FP relay and when it did the exact same thing (buzzed, fluttering on and off) I started to look around harder at other things, and found the loose wire.

petebee said:

Can you elaborate on the alligator clip method? Are you simple making a jumper to connect both sides of the number 6 fuse holder...if so are you saying to leave the fuse in place, or remove it and jumper the connection? Would you recommend putting an inline fuse into the fab'd jumper wire?

I am having a similar problem with my son's 93 240...warm, low speed stalls and trouble with warm engine restarts (stalls when reversing). The fuse holder for #6 is a bit scorched and feels a little warm. The fuel pump relay is a little warm, too. I am thinking resistance in wiring somewhere or a fuel pump going down.

I'll see what ECU he has. Not sure what month the car was built, but I can check that, too.

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Sure. The idea is to bypass the contact resistance between the fuse clips and the ends of the fuse. Just for a test. Using an in-line fuse would be the proper way to do it, but I'm fairly confident that would be just as proper for the 4-6 jumper trick - if one is Volvo-Safe.

Leaving the original fuse in place for the test is optional and made irrelevant by the jumper.

But as yours is the 93, be clear about whether the engine management fuse is early production (in the interior fuse panel) or moved back out under the hood (PAL fuse array attached to positive battery cable). That may have been a reaction to a liability issue to have arisen mid-way in the last year of production. All the Mitchell drawings you see linked on this site show the late production 93 wiring diagram. There are two green WDM versions for that year.

Of course, I was taking advantage of an ideal situation the OP had -- that of being able to get the failure to recur consistently. Nevertheless, anything like this jumper use is bound to disturb the invisible corrosion that is ultimately responsible for the 91 acting different in 2013 than it acted in 1993 with respect to this engine management system main fuse. But if your fuse 6 has visible overheating marks, you've found your problem.

In the end, yes, I think I would recommend replacing that particular fuse with a pigtail fuse holder just like most everyone has where (when) it was located just beneath the hood/fender slot between 1983 and 1990. One of those "marine" blade fuse holders fitted with well-installed (crimp schwartz) female fastons - and a close inspection of the 20 y-o crimps on the harness behind the fuse panel.

It's a Volvo 'best practice' to run your finger down the line of those damned fuses every once in a while - to rotate them in their clips and scrub off non-conductive corrosion.

The PV has only a few of them, out under the hood. They'll stop conducting fairly frequently unless you give them the little roll every couple of months.

cleanflametrap said:

In the end, yes, I think I would recommend replacing that particular fuse with a pigtail fuse holder just like most everyone has where (when) it was located just beneath the hood/fender slot between 1983 and 1990. One of those "marine" blade fuse holders fitted with well-installed (crimp schwartz) female fastons - and a close inspection of the 20 y-o crimps on the harness behind the fuse panel.

Click to expand...

Okay not trying to sound dense, but want to make sure I'm clear. I am 99% certain that there is no fuse in the engine bay...just positive wire running to starter and smaller positive wire running to what looks like a power distribution block on the inner fender. No fuses inline that I can see.

So, I would remove the two wires from the behind the fuse panel connected to the #6 fuse (these have female ends) and install a fused wire jumper (kind you can get at Advance that have a later style inline blade fuse) between the two female connectors. 16 amp fuse, right?